Hybrid-electric vehicles (HEV) utilize components that draw power from a high-voltage power bus and a low-voltage power bus. The source of power for the low-voltage power bus is derived from the high-voltage power bus. When sufficient power cannot be transferred from the high-voltage power bus to the low-voltage power bus, batteries connected to the low-voltage power bus may temporarily provide power but eventually become depleted. Once the batteries are depleted, components drawing power from the low-voltage power bus become inoperable.